Structure Changes of a Membrane Polypeptide under an Applied Voltage Observed with Surface-Enhanced 2D IR Spectroscopy.
Structure Changes of a Membrane Polypeptide under an Applied Voltage Observed with Surface-Enhanced 2D IR Spectroscopy.
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DOI：
10.1021/acs.jpclett.0c03706
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发表时间：
2021-02-25
期刊：
影响因子：
--
通讯作者：
Zanni MT
中科院分区：
文献类型：
--
作者：
Birdsall ER;Petti MK;Saraswat V;Ostrander JS;Arnold MS;Zanni MT
许多膜结合蛋白和多肽的结构取决于膜电位。然而，在应用领域中，光谱研究它们的结构是具有挑战性的，因为很难在多个双层中产生电位。我们研究了膜结合多肽alamethicin的电压依赖性结构，使用涂有粗糙金膜的光谱电化学电池来产生表面等离子体。等离子体激元足以增强二维红外信号来测量单个双分子层。薄膜也足够厚，可以传导电流，从而施加电势。二维红外光谱分析了310-和α-螺旋结构以及连接两者的交叉峰的特征。在施加电压时，我们观察到的是峰值强度的变化，而不是它们的频率。pH值也会发生类似的变化，已知它会改变alamethicin相对于表面法线的角度。用振动激子哈密顿量对光谱进行建模，结果表明，薄膜中310-和α-螺旋的角度分别从55°到44°和从31°到60°的变化与电压相关。310-和α-螺旋的耦合距离约为10 cm−1。这些实验提供了在电位差下alamethicin的新结构信息，并展示了一种可能应用于电压门控膜蛋白和分子动力学结构比较的技术。
The structures of many membrane-bound proteins and polypeptides depend on the membrane potential. However, spectroscopically studying their structures under an applied field is challenging, because a potential is difficult to generate across more than a few bilayers. We study the voltage-dependent structures of the membrane-bound polypeptide, alamethicin, using a spectroelectrochemical cell coated with a rough, gold film to create surface plasmons. The plasmons sufficiently enhance the 2D IR signal to measure a single bilayer. The film is also thick enough to conduct current and thereby apply a potential. The 2D IR spectra resolve features from both 310- and α-helical structures and cross-peaks connecting the two. We observe changes in the peak intensity, not their frequencies, upon applying a voltage. A similar change occurs with pH, which is known to alter the angle of alamethicin relative to the surface normal. The spectra are modeled using a vibrational exciton Hamiltonian, and the voltage-dependent spectra are consistent with a change in angle of the 310- and α-helices in the membrane from 55 to 44°and from 31 to 60°, respectively. The 310- and α-helices are coupled by approximately 10 cm−1. These experiments provide new structural information about alamethicin under a potential difference and demonstrate a technique that might be applied to voltage-gated membrane proteins and compared to molecular dynamics structures.
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